In glassware forming, forming machines commonly known as I.S. forming machines are used, which comprise a number of side by side forming sections, each for producing a respective sequence of products. Each forming section comprises a rough mold, normally comprising a row of side by side cavities, each for receiving a glass gob and forming a respective semifinished article, which is then transferred to a finish mold by means of an inverter. Each rough mold comprises two half-molds movable with respect to each other between a closed position defining the row of cavities, and an open position in which to remove the semifinished articles.
The half-molds are moved between the open and closed positions by means of a mold opening/closing device comprising an actuating arm for each half-mold. The actuating arms are connected at one end to the respective half-molds, and are hinged at the other end to a fixed supporting structure to rotate, in opposite directions and with respect to the fixed structure, about a fixed common hinge axis aligned with and parallel to the row of cavities.
The arms are connected to transmissions activated by respective actuators, which, also for reasons of size, are located at a distance from the mold.
Though widely used, known solutions of the above type have several drawbacks. In particular, the location of the arm hinge axis poses problems when working with a large number of cavities, on account of the cavities not being opened simultaneously and in the same way, due to the different trajectories travelled by the various portions of the half-molds, depending on how far away they are from the hinge axis. And this is reflected in the semifinished articles, which, by the time the molds are open, have different surface qualities and, at times, even different structural characteristics, sometimes bordering on the critical.
Known opening/closing devices are also unsatisfactory in terms of efficiency, particularly when the machine is operated at a high output rate, and are invariably bulky, especially perpendicular to the longitudinal plane of symmetry of the mold. This is mainly due to the transmissions having extremely long torsion shafts for transferring motion from the remote actuator, and which inevitably twist, thus creating unacceptable delays in opening/closing the molds, and unpredictable wear which, once initiated, worsens rapidly and uncontrollably.
Besides being complex and bulky, the transmissions of known solutions are also located alongside or outwards of the arms, thus increasing the size of the mold opening/closing devices crosswise.